如何在Windows中获取窗口的默认标题栏高度

Question

我正在开发一个应用程序，它使用了一个自绘制的标题栏，需要模仿系统默认的标题栏。

那么，如何在Windows中获得被覆盖窗口的默认标题栏高度呢？

Answer 1

从Firefox移植的源代码：

// mCaptionHeight is the default size of the NC area at
// the top of the window. If the window has a caption,
// the size is calculated as the sum of:
//      SM_CYFRAME        - The thickness of the sizing border
//                          around a resizable window
//      SM_CXPADDEDBORDER - The amount of border padding
//                          for captioned windows
//      SM_CYCAPTION      - The height of the caption area
//
// If the window does not have a caption, mCaptionHeight will be equal to
// `GetSystemMetrics(SM_CYFRAME)`
int height = (GetSystemMetrics(SM_CYFRAME) + GetSystemMetrics(SM_CYCAPTION) +
    GetSystemMetrics(SM_CXPADDEDBORDER));
return height;

PS：高度取决于dpi。

Answer 2

一种解决方案是使用AdjustWindowRectEx函数，该函数还计算其他窗口边框宽度，并允许窗口样式变化：

RECT rcFrame = { 0 };
AdjustWindowRectEx(&rcFrame, WS_OVERLAPPEDWINDOW, FALSE, 0);
// abs(rcFrame.top) will contain the caption bar height

对于现代Windows（10+），有一个支持DPI的版本：

// get DPI from somewhere, for example from the GetDpiForWindow function
const UINT dpi = GetDpiForWindow(myHwnd);
...
RECT rcFrame = { 0 };
AdjustWindowRectExForDpi(&rcFrame, WS_OVERLAPPEDWINDOW, FALSE, 0, dpi);
// abs(rcFrame.top) will contain the caption bar height